WASTE BAMBOO FIBER AS A POTENTIAL RESOURCE FOR CELLULOSE ACETATE PREPARATION

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1 Available online at Proceedings of the 1 st International Conference on Engineering Materials and Metallurgical Engineering December, 2016 Bangladesh Council of Scientific and Industrial Research (BCSIR) Dhaka, Bangladesh WASTE BAMBOO FIBER AS A POTENTIAL RESOURCE FOR CELLULOSE ACETATE PREPARATION JuliyaKhanam a,b, M.A. Gafur b, G.M. ArifuzzamanKhan a, J.A.Faisal a, Md. ShamsulAlam a* a Dept. of Applied Chemistry & Chemical Technology, Islamic University, Kushtia, Bangladesh b PP and PDC, BCSIR, Dhaka, Bangladesh ABSTRACT Agricultural wastages, woody biomass and related resources form promising feed stock of cellulose and its derivatives. Biomass from bamboo is such a candidate can offer advantages over some woody biomass as a raw material for cellulose. To explore the potential application of waste bamboo fiber, an investigation was conducted for producing cellulose acetate (CA) in combination with NaClO 2 pulping. Waste bamboo fiber was digested with NaOH solution (17 and 24%) followed by pulping with 1% NaClO 2 solution. Acetylation of bamboo pulp was then carried out with acetic anhydride and acetic acid in presence of concentrated sulfuric acid as catalyst for 15, 45, and 60 min. The degree of substitution (DS) was measured by titrimetric method. It was found that the reaction parameters have great influence on DS. Prepared CA samples are characterized by using various methods such as FTIR, TGA and WAXD. FTIR spectra confirm the formation of ester by acetylation reaction which is more pronounced the condition (24% NaOH treated pulp, 99.8% acetic acid, 99.5% acetic anhydride, 15min). Crystallinity Index (CrI) of prepared CA was measured with respect to standard cellulose samples by using origin 8 software. The minimum CrI65.5% is obtained for the sample which was prepared by 60 min acetylation reaction. However, the thermal stability (onset degradation) of CA was increased with the increases of DS. H OH OHO H O H H OH H glucose unit of cellulose H OCOCH 3 OCOCH 3 COCH 3 O + 3O + 3CH 3 COOH H O COCH 3 H H OCOCH 3 H cellulose triacetate FIG. 1: Reaction between cellulose and acetic anhydride Keywords: Waste bamboo fiber, Cellulose pulp, Cellulose acetate, Degree of substitution, Crystallinity index, Thermal stability 1. INTRODUCTION Cellulose is the main structural ingredient of plants, and is usually considered to be the most common organic compound on earth.it is a renewable and biodegradable substance, providing a cheap source of quality fiber and thousands of derivatives. Cellulose acetate is one of most important derivatives prepared with the reaction of acetic anhydride. Cellulose acetate is particularly used in the clothing industry. It has other applications in various field such as magnetic computer tape, absorbent surgical dressings, some types of adhesives, personal hygiene products, absorbent cloths and wipes, as specialty papers, as filter media, including cigarette filters, photography etc. [1]. Woody plants and cotton were the major sources of cellulose and its derivatives. Bangladesh has enormous volumes of woody biomass that contain cellulosic fibers are generated every year. The cellulose acetate have been prepared from woody biomass such as jute stick, cotton linters, woodchips, rice straw, wheat hull and corn

2 fiber [2-4]. However, value added applications of many agro-wastes are still unexplored for example; bamboo is allowed to rot away. Therefore, attention should be taken to evaluate the potentiality of biomass from bamboo industry for cellulose acetate preparation. Cellulose acetates with different properties are obtained depending on the esterification degree (degree of substitution DS) [5-6]. Cellulose acetate is broadly classified into two types, i.e., cellulose diacetate and cellulose triacetate with acetyl values of about 55% (DS=2.4) and 61% (DS= 2.9), respectively. The solubility of cellulose acetate in a solvent depends on the DS [2]. The appropriate selection of production item and solvent is a key point in using cellulose acetate. In this work, cellulose from bamboo waste fibers are used as cellulose sources for producing cellulose acetate. Normally industrial waste bamboos are considered as domestic fuel. High cellulose and low lignin percentage of bamboo fiber can be potential raw materials for cellulose acetate production. However low substitution of acetate group with cellulose gives low quality product. Thus the aim of the thesis is to improve the experimental conditions of the acetylation reaction in order to increase the DS of cellulose acetate produce from industrial waste bamboo fiber.this work focused the potential use of cellulose to produce cellulose acetate. Cellulose acetate was characterized by Fourier transform Infrared Spectroscopy (FTIR), determination of degree of substitution (DS), thermogravimetric analysis (TGA) and X-ray diffraction (WAXD). 2. MATERIALS AND METHODS The raw bamboo fiber was collected from the local area of Magura district, Bangladesh. The chemicals and reagents were used in this study were purchased from Merck, Germany. 2 gm 24/17% NaOH treated BC +10 ml acetic acid (99.8 and 60%) + 20 ml toluene + 5drops H 2SO 4 (98%) Stirred After 1 min added 10 ml acetic anhydride (99.5%) Stirred vigorously for 15, 45, 60 min Added equal volume of water Dried at room temperature and stored in desiccators Filtered Washed with distilled water Aged about 20 h for partial hydrolysis FIG. 2: FLOW DIAGRAM OF CELLULOSE ACETATE PREPARATION FROM BAMBOO CELLULOSE (BC) 2.1 FIBER PROCESSING The waste bamboo fibers were collected randomly from handicrafts industries and preserved it in a poly bag. The fibers were cut into 2-3 cm small pieces. The fibers were scoured in a solution containing 6.5 g/l of detergent and 3.5 g/l of Na 2 CO 3 at C for 30 min in a large beaker. The ratio of the fiber to solution was maintained at 1: 50. The fibers were thoroughly washed with distilled water and dried in the open air and finally stored in desiccators. 30 g of scoured bamboo fibers are taken in a large beaker and treated with NaOH (17 and 24 w/v%) for 3 h. The fiber to liquor ratio was maintained at 1:20. Then the treated fibers were washed thoroughly several times with dilute acetic acid and distilled water. The fibers were dried in room temperature and stored in desiccators. 10 g alkali treated fibers were bleached with 2% sodium chlorite (NaClO 2 ) solution for 2 h at C. The fiber to liquor ratio was maintained at 1:50. The solution ph 4 was adjusted with dilute acetic acid. A buffer mixture of ph 4 was added upto 10 vol% of total volume of solution. After treatment the bleached fibers were 96

3 filtered over a sintered funnel and washed thoroughly with distilled water. It was then treated with 0.2 wt% sodium metabisulphite (Na 2 S 2 O 5 ) solution for 20 min. The fiber to liquor ratio was maintained at 1:20. Again the fibers were filtered and washed thoroughly with distilled water, dried in an open air and then stored in desiccators [7]. 2.2 PREPARATION OF CELLULOSE ACETATE For the acetylation of cellulose, 2 g of alkali treated bamboo cellulose were taken in10 ml acetic acid (99.8%), 20 ml toluene and 5 drops H 2 SO 4 (98%) and stirred vigorously (Fig. 2). After 1 min 10 ml of acetic anhydride (99.5%) was added and stirred for 15 min at room temperature. Then an equal volume of water was added to the reaction mixture to precipitate cellulose acetate. The reaction mixture was aged 20 h for partial hydrolysis occurs. Then the mixture was filtered, washed thoroughly with distilled water and dried at room temperature. The white color cellulose acetate powder was obtained. For optimization the reaction condition, 99.8% and 60% acetic acid were used and time of acetylation reaction was varied as 15, 45 and 60 min. 2.3 MEASUREMENTS Infrared spectra of cellulose and cellulose acetate (C.A) were recorded with FTIR 8400S Shimadzu spectrophotometer in the range of cm -1 using KBr pellet technique. Appropriate quantity of KBr and sample were mixed by grinding in an agate mortar. Pellets were made with about 100 mg mixture. For better resolution 30 times scans were taken. Wide angle X-ray diffraction (WAXD) pattern of fibers were taken with BRUKER D8 ADVANCE wide angle X-ray diffractometer using Cu Kα radiation (α=0.154 nm), voltage of 50 KV and current of 40 ma with 2θ ranges from 5 to 45 increased in step of 2º/min. The data was analyzed by Origin 8 software. Crystallinity Index was calculated by the following equation [8]: Crystallinity Index (Crl %) = 100 (1) The thermogravimetric analysis (TGA) of cellulose and cellulose acetate are conducted by thermal gravimetric analyzer supplied by TA Instrument. The samples are heated steadily at a rate of 20 K/min from 25 C to 550 Cin nitrogen atmosphere. Degree of substitution (DS) is the average value of the substituted hydroxyl group in the glucosidic units by the acetyl group. It is one of the most important processes to characterized cellulose acetate. It is determined through a saponification process, where a mixture of 75 ml ethanol and 5 ml nitric acid was mixed into 4 g of pulp samples and stirred for min. The samples were then boiled for 5 min and filtered using warm ethanol. Samples were then oven dried at 70 C for 12 h. 0.7 g of the oven dried samples were mixed with 100 ml sulphuric acid and 25 ml of sodium hydroxide 0.5 N and then heated for min. The solution was then titrated using hydrochloric acid 0.5 N, with phenolphthalein as indicator. Equation (1) was used in order to determine the percentage of acetyl groups [9]. DS =.. (2) Where; A = (BC DE) / F B = Volume of sodium hydroxide solution added C = Normality of sodium hydroxide D = Volume of hydrochloric acid required for titration E = Normality of hydrochloric acid F = Weight of cellulose acetate used 97

4 3. RESULTS AND DISCUSSION Sodium hydroxide concentration, acetic acid concentration and the acetylation time are considered the parameters for the preparation of cellulose acetate. Effect of various reaction parameters on cellulose acetate preparation are given in the Table 1. Table 1: Effect of reaction parameter on cellulose acetate preparation Sample (%) of NaOH (%) of CH 3 COOH Time(min) DS CrI (%) Cellulose CA- B CA- C CA- D CA- E CA- cellulose acetate Table 1 shows the change of DS with NaOH concentration, acetic acid concentration and reaction time. It is seen that DS of CA obtain from 17% and 24% alkali treated cellulose are 1.55 and 1.72 respectively. 24% alkali treated cellulose shows higher DS than 17% alkali treated cellulose. It is seems that removal of non-cellulosic part increases with the increase of alkali concentration. Due to contain less amount of non-cellulosic matter in 24% alkali treated cellulose more esterification occurred on cellulosic part. 24% alkali treated cellulose was esterified in presence of 99.8%, and 60% acetic acid for 45 min. It is evident that DS decreases with decrease of acetic acid concentration. At higher concentration acetic acid has great influence of esterification reaction [10]. 24%NaOH treated cellulose were esterified in presence of 99.8% acetic acid for 15 and 60 min and DS are listed at Table 1. It is observed that DS of CA increases with increase of acetylation time. The FTIR spectra of cellulose, CA- B, CA- C, CA- D and CA- E are presented in the Fig. 3. The FTIR spectra of bamboo cellulose contain the typical vibration bands of the components mainly corresponding to cellulose. In the cm -1 region, it is possible to appreciate in fibers vibrations of chemical components of the lignin at frequencies of 1514 cm-1 for guaiacyl and 1468, 1433, and 1214 cm-1 associated with syringyl [11]. These absorptions are consistent with those of the typical cellulose backbone. Furthermore, almost the same absorption peaks were observed in the spectrum of the cellulose acetate samples. The additional peak found at cm -1 for all cellulose acetate is attributed to the ester peak. It has also observed that the intensity of esterification peaks for sample CA- D is very small. This may also reveal esterification rate very low in lower concentration of acetic acid cm Wavenumber (cm -1 ) FIG. 3: FTIR SPECTRA OF (A) CELLULOSE, (B) CA- B, (C) CA- C, (D) CA- D AND (E) CA- E 98

5 The crystallinity index (CrI%) of bamboo cellulose and CA samples have been analyzed by X-ray diffractometry. From the Fig. 4, it is seen that all the cellulose peaks near 2θ=16.2º, 22.2º, and 34.2º. crystallinity index (CrI%) is calculated by peak area calculation using Origin 8 software. There was no crystalline transformation of the crystalline structure in the CA samples due to invisible changes in the diffraction angle (2θ). All the diffractograms of cellulose and CA displayed a strong intensity peak at around 2θ = 22.2 and 16.2, other weak diffractions at 2θ = The percentage of CrI of CA is lower than the cellulose is noted at Table 1. This may be due to deposition of acetylated amorphous components on cellulose surface [12] Diffraction angle (2 ) FIG. 4: WAXD pattern of Cellulose, CA- B, CA- C, CA- D and CA- E The thermal behavior of cellulose and CA samples are presented in the Table 2. For convincing explanation, three different temperature ranges (30-150, , and ) were considered on the basis of the degradation of the constituent of fibers. The first weight loss at the range C is found due to removal of moistures. The further degradation is occurred at the range of C for removal of low molecular weight fraction and final weight loss is happened for degradation of cellulose at the range of C [13]. From the table, it is seen that CA content less amount of moisture then cellulose. Therefore, after acetylation cellulose becomes more hydrophobic. The further degradation is occurred at the range of C. The cellulose and CA samples shows very trace loss in weight. Probably the loss of low molecular weight carbohydrate is caused by hydrolysis with higher concentration of acid. These values proved that bamboo cellulose has neglected quantity of hemicelluloses. The final degradation is occurred at the range of C and respective weight loss is due to degradation of cellulose. The order of weight loss in this range cellulose>ca- C>CA- D> CA- B>CA- E. Table 2: Weight loss of bamboo cellulose and CA samples at various temperatures Sample Wt. loss (%) at C Wt. loss (%) at C Wt. loss (%) at C Cellulose CA B CA- C CA- D CA- E

6 1600 (A) 15 (B) DTG ( g/min) DTA Temperature ( C) Temperature ( C) FIG. 5: DTG (A) and DTA (B) of cellulose, CA- B, CA- C, CA- D and CA- E Fig. 5(A) shows the rate of thermal decomposition (DTG) of cellulose and cellulose acetate samples. The first decomposition peak around C for all the samples are found due to the removal of moisture and the broad degradation observed at C may be due to decomposition of main chain as well as substituted groups of cellulose. It has been evident that the peaks at C for samples CA- B and CA- E exhibit two-step degradation. This may because of the addition of acetate group in cellulose chain. The endothermic changes are given away at Fig. 5(B). The samples CA- B and CA- E also show the additional endothermic peaks around 270 C. 4. CONCLUSION Heterogeneous acetylation of bamboo cellulose was successfully performed in the presence of sulfuric acid as a catalyst. The cellulose acetate samples exhibit almost similar trend in WAXD diagram as cellulose. The percentage of CrI of all cellulose acetate samples is lower than the cellulose. The crystallinity and thermal properties of prepared cellulose acetate samples is highly dependent on degree of substitution. However, hydrophobic character of the cellulose was increased by acetylation. The acetylated cellulose fibers are more susceptible to thermal degradation than that of bamboo cellulose. The acetylated celluloses exhibit dissimilar rate of degradation and endothermic nature. 5. REFERENCES [1] Chowdhurey J and Khan G M A. Utilization of Sawmill By-Product for Making Cellulose and Its Valuable Derivatives.Biomass and Bioenergy: Applications, Edited by K.R. Hakeem et al. (eds, 07/2014; Springer International Publishing Switzerland., ISBN: ISBN (ebook). [2] Tanghe L J, Genung L B and Mench J W, In Advances in Carbohydrate Chemistry, Academic Press, 1963, 193. [3] Umoren S A., Umoudoh A J and Akpabio, UD, 2004, Bulletin of Pure and Applied Sciences, 2004, 23, [4] Li J, Xie W, Cheng H N, Nickol R G and Wang P G, Macromolecules, 1999,32, [5] Zhou X, Lin X, White K L, Wu H, Cao S, Huang L and Chen L. Effect of the degree of substitution on the hydrophobicity of acetylated cellulose for production of liquid marbles. Cellulose, 2016, 23: 811. [6] FISCHER S, THÜMMLER K, VOLKERT B, HETTRICH K, SCHMIDT I AND FISCHER K. PROPERTIES AND APPLICATIONS OF CELLULOSE ACETATE. MACROMOLECULAR SYMPOSIA, 2008, 262: [7] KhanGMA, HaqueMA, TeranoM and AlamM. Graft polycondensation of microfibrillated jute cellulose with oligo (L lactic acid) and its properties. Journal of Applied Polymer Science, 2014, 131(8):

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